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Thread: Evohome and Combi Power usage

  1. #1
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    Default Evohome and Combi Power usage

    Since having the combi fitted with Evohome my electric month on month has more than doubled. Gone up from an average 160kwh to 340 a month.

    Any ideas?

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    Quote Originally Posted by robj20 View Post
    Since having the combi fitted with Evohome my electric month on month has more than doubled. Gone up from an average 160kwh to 340 a month.

    Any ideas?
    A possible contributory cause is longer pump ON times as Evohome manages heating in less of a stop/start way. That said, an extra 6kWhs/day is somewhat extreme. Looking at my boiler manual, the pump has a maximum wattage of 96watts which, if it was running at full pelt for 24 hours, would only equate to about 2.3kWhs/day in total.

    I have seen comments on other forums suggesting that a possible cause of continuous pump running is because someone has enabled the boiler's frost protection.

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    Quote Originally Posted by HenGus View Post
    A possible contributory cause is longer pump ON times as Evohome manages heating in less of a stop/start way. That said, an extra 6kWhs/day is somewhat extreme. Looking at my boiler manual, the pump has a maximum wattage of 96watts which, if it was running at full pelt for 24 hours, would only equate to about 2.3kWhs/day in total.

    I have seen comments on other forums suggesting that a possible cause of continuous pump running is because someone has enabled the boiler's frost protection.
    The manual says a max of 137w.
    I calculate the 158kwh a month to be about 210w so it's somebody using a lot of power. Going to get a cheap clamp on meter and starting going round turning things off.

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    Quote Originally Posted by HenGus View Post
    A possible contributory cause is longer pump ON times as Evohome manages heating in less of a stop/start way. That said, an extra 6kWhs/day is somewhat extreme. Looking at my boiler manual, the pump has a maximum wattage of 96watts which, if it was running at full pelt for 24 hours, would only equate to about 2.3kWhs/day in total.

    I have seen comments on other forums suggesting that a possible cause of continuous pump running is because someone has enabled the boiler's frost protection.
    I read robj20's post as saying he had had Evohome installed and a new boiler at the same time. So I don't know how anyone could conclude that Evohome might be responsible. Perhaps the old system had no pump overrun at all, if it was a very old system. (My system had no pump overrun until I added a timer...)

    However as you've calculated even a pump running 24/7 using 96 watts, (mine uses less than 30 watts on the low speed I have it set to) would only approach 1/3rd of the increase in electricity being reported.

    So I simply fail to see how it could be the heating system at all unless there is also some electric heating involved. The intermittent usage of a pump especially a modern low energy permanent magnet type would be negligible on a monthly power bill.

    I'd be looking elsewhere in the house for the explanation - I'd start by getting something like a loop energy saver which clamps onto the cable in the meter box to monitor and graph overall household usage to see what the overall power draw is at given times of the day and spot any trends, and I'd also invest in a few 10 3 pin kWh meters to put on individual appliances such as dish washer, washing machine etc to see how much they are using.

    I wonder if robj20 has an electric shower (as we do) or anything else that could use a lot of electricity. A few months ago I bought an electric car and use it for a 1000 mile per month daily commute and it still only increased my power bill by 30%!

  5. #5
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    I do have an electric shower but nothing has changed other than a new boiler in the last month. Going to get a meter thing an Owl monitor. See what that shows.

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    Quote Originally Posted by robj20 View Post
    I do have an electric shower but nothing has changed other than a new boiler in the last month. Going to get a meter thing an Owl monitor. See what that shows.
    Do you have kids who have perhaps decided long showers are good in cold weather ? An electric shower is 10kW typically so the difference between 10 minute showers and 20 minute showers on the bill at the end of the month can be a lot...

    I've been using the loop energy saver for nearly a year now and find it great. More than just measuring the present usage it will graph it on an hourly basis and makes it easy to see daily, weekly, monthly trends etc. And it will calculate how much you're paying per day/week/month if it knows your tariff. The monthly figures it reports are within about 10% of what my energy provider puts on my invoice. I also use it to monitor gas usage.

    Having this kind of feedback certainly helped to modify our habits when we saw immediate daily feedback on usage, both gas and electricity. For example when scheduling heating in different rooms it's surprising how much gas you can save by having lesser used rooms that you don't spend much time in (for example bathroom in the evening) 1-2 degrees lower in temperature. If you only get a bill at the end of the month you can never correlate what you did with what generated a large bill.
    Last edited by DBMandrake; 9th October 2017 at 10:10 AM.

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    @DBMandrake

    Hence my use of the word 'contributory'. I agree that some simple checks around the house are needed before blaming Evohome. The OP may wish to clarify whether it is a new boiler and Evohome, or an existing system to which Evohome has been added? I would though check that permanent frost protection hasn't been enabled and then, as you suggest, go back to basic tests. I appreciate that all boilers are different but most modern boilers allow the user to set the pump to run continuously if the boiler is not often used or it is located in a very cold outhouse. The cost/benefit of doing so has come up a few times on forums where people have second homes/ properties that they let out in the summer time.

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    Quote Originally Posted by DBMandrake View Post
    Do you have kids who have perhaps decided long showers are good in cold weather ? An electric shower is 10kW typically so the difference between 10 minute showers and 20 minute showers on the bill at the end of the month can be a lot...

    I've been using the loop energy saver for nearly a year now and find it great. More than just measuring the present usage it will graph it on an hourly basis and makes it easy to see daily, weekly, monthly trends etc. And it will calculate how much you're paying per day/week/month if it knows your tariff. The monthly figures it reports are within about 10% of what my energy provider puts on my invoice. I also use it to monitor gas usage.

    Having this kind of feedback certainly helped to modify our habits when we saw immediate daily feedback on usage, both gas and electricity. For example when scheduling heating in different rooms it's surprising how much gas you can save by having lesser used rooms that you don't spend much time in (for example bathroom in the evening) 1-2 degrees lower in temperature. If you only get a bill at the end of the month you can never correlate what you did with what generated a large bill.
    Nope no kids at all just the two of us. If anything there have been less showers this month.

    Ordered an Owl Micro+ monitor, see start that shows tonight.
    Last edited by robj20; 9th October 2017 at 10:16 AM.

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    Quote Originally Posted by robj20 View Post
    Nope no kids at all just the two of us. If anything there have been less showers this month.

    Ordered an Owl Micro+ monitor, see start that shows tonight.
    That's a bit extreme. Most libraries now hold energy saving kits with monitors. Personally, I would start turning things off /checking the meter first before going down the monitor route.

  10. #10
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    The Smappee energy monitor is good. It can (with certain limitations) identify the individual devices consuming electricity in your home.

    It isn't perfect - it can't distinguish between my oven and my microwave, for example, but overall it works well. You just need to leave it for a couple of weeks to 'learn' your house. Much like with Evohome, if you start fiddling too soon you get sub-optimal results.

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